Chipper cutter and holders therefor

ABSTRACT

When installed on the cylindrical cutter surface of the chipper drum, the cutter presents a knife having an arcuate cutting edge thereon, the relatively concave face of which is described by a surface revolution, and the relatively convex face of which has a plurality of facets described by angularly successive pairs of dihedral planes passing through the concave face of the edge at acute angles thereto, so that the edge is scalloped in outline. The knife is formed on an annular blade having a plurality of such knives at angularly spaced locations thereabout; and the blade is defined by one end edge portion of an elongated tubular element which is installed in either a socket-like holder or a saddle-like holder, having means thereon whereby the element can be alternately releasably interlocked with the holder in a relative longitudinal position presenting one knife, or released and rotated to present another knife, in the same or a different such position.

United States Patent [191 Anson Jan. 14, 1975 [54] CHIPPER CUTTER ANDHOLDERS THEREFOR [76] Inventor: IAnson Anson, 4014 Hunts Point Rd.,Bellevue, Wash. 98004 [22] Filed: May 8, 1972 [21] Appl. No.: 251,519

Related US. Application Data [62] Division of Ser. No. 75,154, Sept. 24,1970, Pat. No.

[52] US. Cl 144/172, 144/241, 241/93 [51] Int. Cl B27l 11/02 [58] Fieldof Search...... 144/172, 162, 241; 83/831; 241/91, 93, 293

[56] References Cited UNITED STATES PATENTS 2,746,494 5/1956 Cox 83/8313,327,746 6/1967 Andrus et a1. 144/241 3,661,192 5/1972 Nicholson et al144/172 Primary Examiner-Donald R. Schran Attorney, Agent, orFirm-Christensen, OConnor, Garrison & Havelka [5 7] ABSTRACT spacedlocations thereabout; and the blade is defined by one end edge portionof an elongated tubular element which is installed in either asocket-like holder or a saddle-like holder, having means thereon wherebythe element can be alternately releasably interlocked with the holder ina relative longitudinal position presenting one knife, or released androtated to present another knife, in the same or a different suchposition.

26 Claims, 19 Drawing Figures g ll z 6:7 -24 PATENTEU JAN 1 41915 sum10F 4 CHIPPER CUTTER AND HOLDERS THEREFOR CROSS-REFERENCE TO RELATEDAPPLICATION This application is a division of a copending applicationentitled CHIPPER CUTTER AND HOLDERS THEREFOR, Thomas IAnson, applicationSer. No. 75,154, filed Sept. 24, 1970, now US. Pat. No. 3,675,693.

FIELD OF THE INVENTION This invention relates to cutter elements andcutter assemblies for rotary chipper drums; and in particular, toelements and assemblies of this nature which are individually equippedwith two or more knives that can be alternately or interchangeablypresented to the woodstock.

Background of the Invention Including Certain Objects Thereof In thewood reduction industry, so-called chipper drums are employed to reducepieces of woodstock such as peeler cores or lily pads, to a mass ofelongated chips, which may or may not be subjected to further reductionthereafter. The drums are generally mounted on inclined axes, andequipped with a series of helically staggered, transversely orientedcutter elements on the outside cylindrical surfaces thereof. The cutterelements have knives thereon which project relatively outwardly from thesurfaces of the drums, so as to progressively longitudinally strip theoutlines of the pieces of woodstock as they are fed radially inwardly ofthe drums while resting on anvils in longitudinally juxtaposed positionsadjacent thereto. heretofore the knives have had an angularly arcuatecutting edge which is rectilinear in outline and characterized with aplurality of facets on each face thereof, described by angularlysuccessive pairs of dihedral planes meeting at acute angles to oneanother, from one face to the other, to give the knives a channel-likeconfiguration when viewed on edge. Such a configuration has not provento be particularly durable, however, since the cutting edges areconsiderably weakened by the angled form of the inside or relativelyconcave faces of the edges, and it has been found that the cutterelements must be frequently removed from the drum sometimes even morefrequently than once a day to resharpen or replace them when they becomedull or broken as a result of the punishment they receive in use. Notonly is it costly and time consuming to have to resharpen or replace theelements with this frequency; but in addition, the resharpeningoperation itself is further complicated by the necessity for grindingand polishing the inside faces of the knives first, that is, before theoutside faces are ground and polished, in order to provide a referenceagainst which to determine the bevel given the outside faces of theknives. The resharpening operation is also complicated by the fact thatthe cutter elements must be set up in three different positions whengrinding the knives; and then backed up with babbitting or the like whenthey are returned to the drum, in order to compensate for the loss ofreach in the cut of the knives, due to the loss of metal in the grindingoperation. The channel-shaped configuration of the knives also tends tocause the stripped wood material to undergo curling as it exits throughthe cutter elements into the drum; and moreover, renders the cutterelements difficult to mount in the drum, and particularly to hold or fixin position and orientation so that they will not degenerate the chipform by working themselves loose in their mountings.

With this in mind, one object of the present invention is to provide acutter element which presents a knife having a stronger and more durableedge configuration, and one which is also less susceptible to breakagethan the edge configurations of the prior art elements. Another objectis to provide a cutter element of this nature which presents a knifehaving an edge configuration that is cheaper and easier to obtain, andalso more easily and cheaply resharpened, so that the elements can bereturned to the drum more quickly, and at lower cost, than were theprior art elements. A further object is to provide a cutter element ofthis nature which produces a better and more efficient cutting action,and which is easier to mount or install on the drum, and to hold inplace during the resharpening operation; and which moreover is adaptedto be more readily and securely returned to its proper position andorientation on the drum, from points outside thereof, and without thenecessity for using babbitting or the like to compensate for thegrinding operation. Still another object is to provide a cutter elementof this nature which presents a knife having an edge configuration thatlends itself to honing techniques for resharpening; and which has areduced number of facets to be resharpened; and the inherent capacity tomaintain substantially its original edge thickness when resharpened. Astill further object is to provide a cutter element of this nature whichlends itself to the provision of two or more knives on the same element,or in the same assembly; and moreover, to the provision of such anelement or assembly which has a plurality of knives that can bealternately or interchangeably presented to the woodstock, as forexample, by shifting the respective element and a holder for the same,in relation to one another, on the surface of the drum. Other objectsinclude the provision of a cutter and holder assembly of this naturewhich enables the cutter element to be alternately fixed and shiftedwith respect to the holder, with equal ease and speed, and to be firmlysecured in the relatively fixed position thereof, without causinginterference to the cutting operation, nor to the steady flow of thewood strips and chips therethrough. They also include the provision ofan assembly of this nature in which the holder for the cutter elementmay comprise one or more components which are also serviceable in theresharpening operation, as for example, in holding the cutter element inplace during the same. Still further objects will become apparent fromthe description of the invention which follows hereafter.

SUMMARY OF THE INVENTION These objects and advantages are realized by achipper cutter of my invention which presents or projects a knife to thewoodstock, having an arcuate cutting edge thereon, the relativelyconcave face of which is described by a surface of revolution, as forexample, a conical or cylindrical surface of revolution. Preferably, therelatively concave face of the edge extends over a continuous arcuatecourse bounded by the cylindrical surface plane of the drum; and iscurvilinear in outline, as for example, where the relatively convex faceof the edge has a plurality of facets thereon, described by angularlysuccessive pairs of dihedral planes passing through the concave face ofthe edge at acute angles thereto, so that the edge is scalloped inoutline.

The knives project relatively outwardly from the surface of the drum onaxes of revolution coincident with progressively helically advancedchords of the drum. Those facets of the relatively convex faces of theedges which traverse the cross-sectional planes of the drum coincidentwith the chords, are disposed in planes which extend substantiallyparallel to the cylindrical surface plane of the drum; and the facetsadjacent thereto are disposed in planes which extend at equal obtuseangles thereto and intersect the cylindrical surface plane of the drum.

Each knife is defined by an annular cutter blade that is seated in arecess in the surface of the drum, and equipped with a plurality ofsimilar knives thereon, at angularly spaced locations thereabout. Theblade is rotatable about the axis thereof between a plurality of angularorientations corresponding to the locations of the knives, and there aremeans interconnecting the blade and the drum whereby the blade can befixed in the seated position thereof at each orientation, for alternateor interchangeable use of the knives thereon. The blade is defined byone end edge portion of an elongated tubular element which is detachablyinserted in the recess and releasably interlockable with the drum ateach operative orientation of the blade. The recess is defined by astationary holder in the surface of the drum, and the element and holderhave cooperable means thereon for fixing the relative angular andlongitudinal positions of the element in the holder at the variousoperative orientations of the blade. These means include cooperating pinand groove means for fixing the position of the holder in one sense, andmeans threadedly interconnected with the holder to fix the position ofthe element in the other sense. For example, the element and recess mayhave cooperatively engaged threading thereon for fixing the longitudinalposition of the element;'or there may be a finger-like retainer memberinserted in the hollow core of the element, and means threadedlyinterconnected to the holder which operate to releasably clamp theelement between the holder and the retainer member.

The retainer member is inserted in the knived end edge portion of theelement and secured to the holder at a point between the one end edge ofthe element and the cylindrical surface plane of the drum. Also, theretainer member is secured to the holder at a point in which it isspaced apart from the one end edge of the element, to enable the elementto be shifted relatively toward the aforesaid point, when it isunclamped. For example, the element may be fixed against relativerotation by a pin on the holder which is received in a groove in theopposite end edge portion of the element, and the space between theretainer member and the element may be such that shifting the elementtoward the point disengages the pin from the groove and thus frees theelement for rotation.

BRIEF DESCRIPTION OF THE DRAWINGS These features will be betterunderstood by reference to the accompanying drawings which illustratetwo of the presently preferred embodiments of the invention.

In the drawings,

FIG. 1 is a part cross sectional operation view of a chipper drumemploying a helically staggered array of socket-held tubular cutterelements characterized with beveled cylindrical blades; 1

FIG. 2 is a part plan view of the drumand a pair of adjacent cutterassemblies of this type therein;

FIG. 3 is a part longitudinal cross sectional view of the drum along theline 3-3 of FIG. 1, illustrating one such assembly in use;

FIG. 4 is a front elevational view of the cutter element in theassembly;

FIG. 5 is a part side elevational view of thecutter element in FIG. 4,along the line 55 thereof;

FIG. 6 is another such view of the element along the line 6-6 of FIG. 4;

FIG. 7 is a perspective view of the socket-like holder for the element;

FIG. 8 is a part cross sectional operational view of a chipper drumemploying tubular cutter elements which are clamped in saddles andcharacterized with beveled conical blades;

FIG. 9 is a perspective view of one of the latter assemblies;

FIG. 10 isa part plan view of the saddle-like holder for the cutterelement in this assembly;

FIG. 11 is a perspective view of a finger-like clamp retainer used inconjunction with the holder;

FIG. 12 is a part plan view of the assembly;

FIG. 13 is a part longitudinal cross sectional view of the assembly whenit is installed on the drum with the cutter element clamped in positionfor use;

FIG. 14 is a similar view of the assembly on the drum with the cutterelement released for rotation to a new operational setting of the bladeon the same;

FIG. 15 is a part cross sectional view along the line 1515 of FIG. 13;

FIG. 16 is a front elevational view of the cutter element in theassembly of FIG. 8; l

FIG. 17 is a side elevational view of the cutter element in FIG. 16along the line 17-17 thereof;

FIG. 18 is another such view of the element along the line 18l8 of FIG.16; and

FIG. 19 is a longitudinal cross sectional view of the elementillustrating one mode of sharpening the same.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, itwill be seen that in each embodiment, the cutter drum 2 has a series ofapertures 4' or 4" in the exterior wall'6 thereof which are spaced apartat equal intervals along a helical course about the longitudinal orrotational axis of the drum. The apertures 4 in turn have acorresponding number of cutter assemblies 8 installed therein, so as torender the drum serviceable as a chipper for a length of woodstock 10which is passed relatively longitudinally abreast thereof and advancedrelatively radially inwardly of the drum as the wood material is reducedto a mass of elongated chips 12. Each cutter assembly 8 comprises atubular cutter element 14' or 14", and a holder 16' or 16" for the samewhich is slidably insertable in the aperture 4 for the assembly, from apoint thereopposite within the drum; and adapted to be thereafter weldedor otherwise secured to the drum 2 while projecting flange abutments 18or 18" on the holder (FIGS. 1 and 9) operate to fix the condition of theholder in the aperture flush with the outside cylindrical cutter surface6' of the drum. The individual cutter elements 14 are detachablyengageable, as well as detachably interlockable with their respectiveholders 16; and when engaged and locked in the holders, are presented tothe Woodstock on equal, angularly successive chordal angles to thesurface 6 of the drum, with the forward, beveled end edge portions 19 or19" of the same projecting in part relatively outwardly from the surface6 of the drum to serve as thumbnail-like, part annular knives 20' or 20for the chipper function, as shall be explained. In addition, thespacing between elements 14 of the respective assemblies is such thatthe knives 20 cut through the outline of the Woodstock in longitudinallysuccessive tangential courses having a slight degree of overlap with oneanother, so as to remove successive parallelogrammaticallycrosssectioned strips 22 of the stock which in turn break intolongitudinal segments or chips 12 of the same within the hollow cores24' or 24" of the tubular cutter elements.

Referring now in particular to the embodiment of FIGS. 1-7, it will beseen that the apertures 4 in the drum are rectangular in planconfiguration; and the cutter element holders 16 installed in the sameare basically angularly truncated tubes 16' having threaded cylindricalsockets 25 therein, and sloped, stepped raised orthogonal crests 26 anddepending heels 28 on the rearward and forward end portions thereof,respectively. The coplanar faces 30 of the steps on the respectivecrests and heels of the holders are formed at the inside radius of thedrum; whereas the oppositely disposed, radially extending faces 32 ofthe steps are spaced apart by the longitudinal dimension of theapertures, to enable the holders to slidably engage in the apertures asmentioned.

The tubular cutter elements 14' employed in the embodiment of FIGS. 1-7are complementally sized and exteriorly threaded to engage in thesockets 25 of the holders 16'; and have longitudinally extending grooves34 in the threaded cylindrical outer surfaces 36 thereof, which arelocated at 90 intervals about the circumferences of the elements so thatthey can be detachably interlocked with the holders in four similarlyspaced orientations, by means of set screws 38 threaded into radiallyextending bores 40 in the crests 26 of the holders. When installed, theelements 14 are threaded into the holders, and interlocked with thesame, at relative longitudinal positions in which the for ward end edgeportions 19' of the elements project in part relatively outwardly fromthe surface 6' of the drum to form arcuate or part annular knives 20' asindicated. The knives 20' are replaceable by, or interchangeable with,three other similar such knives 42 which are disposed in angularrelationship thereto about the circumferences of the forward end edgeportions, but normally withdrawn relatively within the sockets 25 of theholders when the knives 20 are in use. The inside or concave cuttingedge faces of the resulting blades 20', 42 are coincident with theinside cylindrical surfaces 44 of the cutter elements; whereas therelatively convex cutting edge faces of the blades have alternate facets46 and 48 described by angularly successive pairs of dihedral planespassing through the cylindrical surfaces 44 of the elements at acuteangles thereto. See FIG. 3 in particular. The bevel of the facets 46 and48, and the relative dihedral angles thereof, is such that the cutterelements present knives 20 or 42 of three full facets 48, 46, 48 each,at each of the 90 intervals corresponding to the locations of thegrooves 34. For example, the facets 46 with center lines at the 90locations, may be beveled at an angle of 30; whereas the intermediatefacets 48 therebetween may be beveled at an angle of 23 on center linesof 45 each, as illustrated in FIGS. 4-6. Preferably, the bevelingoperation is performed in opposite sequence, however, so that therespective facets are delimited by planes extending parallel to axialplanes of the elements at the 90 locations. See FIG. 4.

When the knife 20' presented by an element 14' at one 90 orientationbecomes blunted or otherwise worn in use, a new knife 42 can bepresented to the woodstock 10 by rotating the element through a 90interval. This operation is performed quite simply by withdrawing thesetscrew 38, and then rotating the element through the interval in thedirection of withdrawing it from its holder 16' in the relativelyoutward direction of the drum. Given a fine gauge threading between theelements and holders, the quarter turn need only have the effect ofadvancing the cut that is, increasing the depth of the cut by a smallorder of magnitude, such as one-sixteenth inch, which is well within theoptimum strip thickness of three-eights inch prescribed for pulpchippers.

In the embodiment of FIGS. 8-19, the holders are also basicallyangularly truncated tubes 16", but the tubes have a two-part crosssection, and are greatly re lieved over the truncated face 50 thereof toform slotted, shoe-like recesses or saddles 52 for the cutter elements14". Also, the elements 14" are detachably engaged and interlocked withthe holders through the use of interchangeable pin and slot connections54 (FIG. 12) at the rear ends of the assemblies, and capscrewed,finger-like clamp retainer members 56 at the forward ends of the same.

The bottom rear end portions 58 of the holders, and the rear endportions 60 of the elements, have complemental part cylindrical and fullcylindrical, inside and outside surfaces, respectively, for resting theelements in the holders; and affixed upright on the bottoms of thesaddles, at center locations, are pins 62 which project inward of theholders just forward of inwardly directed flanges 64 on the rear endsthereof. The pins 62 cooperate with longitudinally relieved slots 66 inthe rear ends of the elements, at 90 locations thereabout; and togetherwith the flanges 64, enable the relative longitudinal and angularpositions of the elements to be fixed in the saddles 52 of the holders,at selected 90 intervals, simply by abutting the elements against theflanges at each orientation in which the pin 62 of the respective holderengages with a slot 66. The bottom intermediate portions 68 of theholders, and the forward end portions 19" of the elements, havecomplemental, axially inwardly inclined, part conical and full conicalcross sections, respectively, the inside and outside surfaces of whichhave alternate facets 70 and 72, or 74 and 76, which are complementallydescribed by angularly successive pairs of dihedral planes on 10V2 and15 angles to the rear end portions 58 and 60 thereof. The forward endportions 78 of the holders continue the part conical bottom section ofthe intermediate portions 68 of the same, but are reinforced by slopedheels 80 depending therefrom. The inside surfaces of the forward endportions 78 are shaped to complement the part-conical undersides 94 ofthe screw-down portions 82 of the retainer members 56 when the latterare inserted into and clamped over the bladed end edge portions 19" ofthe cutter elements. Threaded bores 84 in the forward end portions ofthe holders serve toreceive the cap screws 86 for this purpose.

Pairs of laterally projecting lugs 18" on the respective forward andrearward end portions of the holders serve as flange abutments for theinstallation procedure explained earlier.

As in the earlier embodiment, the bladed forward end portions 19" of thecutter elements are beveled at their edges to form a plurality of knives20" which are angularly related about the circumference thereof; but inthis instance, the pairs of dihedral facets 74 and 76 on the edges ofthe elements are beveled back the full depth of the portions 19",whereas the relatively concave faces 88 of the edges are described byconical surfaces of revolution at acute angles to facets 74, 76, andobtuse angles to the inside surfaces 90 of the portions 19". In thisway, the edges of the elements can be sharpened from the inside, as forexample, by using a complementally shaped honing wheel 92 (FIG. 19)which is inserted in the bladed end portions 19" of the elements for thepurpose. Preferably, the facets 74 at the 90 intervals corresponding tothe locations of the slots 66 are beveled at the previous indicatedangle of and the intermediate facets 74 at 105?; while the conicalinside faces 88 are honed at a reverse angle of l5 to establish a 30edge, as in the earlier embodiment.

The upper sides 96 of the screw down portions 82 of the retainer members56 are sharply inclined, and the members are equipped with countersunkholes 98 for the cap screws 86, so that the portions 82 are flush withthe cylindrical surface 6 of the drum in the clamped condition of theassemblies 8, and the heads 100 of the cap screws are fully accommodatedwithin the members. The hold-down portions 102 of the members have bentor crooked finger-like configurations corresponding to the obtuse anglebetween the surfaces 88 and 90 of the cutter elements; andare partconical, and then part cylindrical at the truncated tips thereof, sothat the relatively rearward joints 104 of the portions 102 mate withthe inside conical and cylindrical surfaces 90 and 108 of the cutterelements. The relatively forward.

joints 106 of the portions interconnect with the screwdown portions 82of the members at a reverse obtuse angle, and for the most part,accommodate the holes 98 for the cap screws.

The cutter elements are fixed in the saddles 52 of the holders byscrewing down the retainer members into the clamped condition of FIGS. 8and 13. As seen, however, the screw-down portions 82 of the members areclamped to the holders at points in which they are spaced forwardly fromthe conical edge faces 88 of the cutter elements, to allow the elementsto be partially withdrawn, that is, shifted forward in the relativelyoutward direction of the saddles, within the gaps 110, when the capscrews 86 are loosened. See FIG. 14. Moreover, the gaps 110 havesufficient distance to enable the cutter elements to be disengaged fromthe pins 62 when they are withdrawn in this manner within the saddles.Therefore, to present a new blade to the Woodstock 10 when the blade inuse becomes blunted or otherwise worn, it is only necessary to loosenthe respective cap screw 86, and to pull the accompanying cutter elementforward, before it is rotated into the orientation of the new blade, andre-engaged with the pin 62 in its holder.

The retainer members 56 also provide a relatively smooth surfacedfeeding platform for the strips 22, to prevent gouging the Woodstock,and to prevent plugging of the cutter elements with knots or the like inthe stock. Moreover, when a cutter element is removed for resharpening,the corresponding retainer member in the assembly can be used to clampit in position for the sharpening operation.

It will be noted that because of their scalloped outlines, the cuttingedges of the knives 20 or 20 effect a slicing or scything action as theycut into the woodstock. This is to say, the curved, progressivelyreceding outlines of the edges contact the wood, first, at the pointeddihedral corners thereof, and then in progressively greater lengthwiseincrements of the same in the direction away from the corners, so thateach knife shears across the fibers of the wood in point-to-pointfashion, rather than meeting the fibers all points at once. Also, duringthis action, the tendency of the knives is to pull the wood into thecutter elements, so that the strips 22 are removed from the stock asfast as the edges of the knives effect severance.

Like the cutter element in the embodiment of FIGS. 8-19, the element inFIGS. 1-7 can be sharpened by inside honing. However, the former has theadvantage that the facets of the same can be beveled back to a greaterdepth and thus provide more metal with which to work in the resharpeningoperation. Moreover, resharpening the element of FIGS. 8-19 does notreduce the wall thickness of the element, so that all told, the elementof FIGS. 8-19 remains serviceable over a longer period of time.

What is claimed is:

l. A rotary chipper drum having a series of cutter knives on thecylindrical cutter surface thereof, each of which projects relativelyoutwardly from the surface of the drum, and has an arcuate cutting edgethereon, the relatively concave face of which is described by a coni- Vcal surface of revolution.

2. The rotary chipper drum according to claim 1 wherein the relativelyconcave face of the cutting edge extends overa continuous arcuate coursebounded by thecylindrical surface plane of the drum.

3. The rotary chipper drum according to claim 1 wherein the relativelyconvex face of the cutting edge has a plurality of facets thereon,described by angularly successive pairs of dihedral planes passingthrough the concave face of the edge at acute angles thereto, so thatthe edge is scalloped in outline.

4. The rotary chipper drum according to claim 3 wherein the knivesproject relatively outwardly from the surface of the drum on axesofrevolution coincident with progressively helically advanced chords ofthe drum.

5. The rotary chipper drum according to claim 4 wherein those facets ofthe relatively convex faces of the edges which traverse thecross-sectional planes of the drum coincident with the chords, aredisposed in planes which extend substantially parallel to thecylindrical surface plane of the drum; and the facets adjacent theretoare disposed in planes which extend at equal obtuse angles thereto andintersect the cylindrical surface plane of the drum.

6. The rotary chipper drum according to claim 3 wherein each knife isdefined by an annular cutter blade that is seated in a recess in thesurface of the drum, and equipped with a plurality of similar knivesthereon, at angularly spaced locations thereabout.

7. The rotary chipper drum according to claim 6 wherein the blade isrotatable about the axis thereof between a plurality of angularorientations corresponding to the locations of the knives, and there aremeans interconnecting the blade and the drum whereby the blade can befixed in the seated position thereof at each orientation, for alternateor interchangeable use of the knives thereon.

8. The rotary chipper drum according to claim 7 wherein the blade isdefined by one end edge portion of an elongated tubular element which isdetachably inserted in the recess and releasably interlockable with thedrum at each operative orientation of the blade.

9. The rotary chipper drum according to claim 8 wherein the recess isdefined by a stationary holder in the surface of the drum, and theelement and holder have cooperable means thereon for fixing the relativeangular and longitudinal positions of the element in the holder at thevarious operative orientations of the blade.

10. The rotary chipper drum according to claim 9 wherein the means forfixing the positions of the element include cooperating pin and groovemeans for fixing the position of the element in one sense, and meansthreadedly interconnected with the holder to fix the position of theelement in the other sense.

11. A rotary chipper drum having a recess in the cylindrical cuttersurface thereof, means defining an annular blade which is seated in therecess and rotatable about the axis thereof, there being a plurality ofknives at angularly spaced locations about the blade, and meansinterconnecting the blade and drum whereby the blade can be fixed in theseated position thereof at orientations corresponding to the locationsof the knives, said knives having an arcuate cutting edge thereon, therelatively concave face of which is described by a conical surface ofrevolution.

12. The rotary chipper drum according to claim 11 wherein the axis ofthe blade is coincident with a chord of the drum, so that a knifeprojects relatively outwardly from the surface of the drum at eachorientation of the blade.

13. The rotary chipper drum according to claim 12 wherein the blade isdefined by one end edge portion of an elongated tubular element which isdetachably inserted in the recess and releasably interlockable with thedrum at each operative orientation of the blade.

14. The rotary chipper drum according to claim 13 wherein the recess isdefined by a stationary holder in the surface of the drum, and theelement and holder have cooperable means thereon for fixing the relativeangular and longitudinal positions of the element in the holder at thevarious operative orientations of the blade.

15. The rotary chipper drum according to claim 14 wherein the means forfixing the positions of the element include cooperating pin and groovemeans for fixing the position of the element in one sense, and meansthreadedly interconnected with the holder to fix the position of theelement in the other sense.

16. The rotary chipper drum according to claim 13 wherein the relativelyconvex face of the cutting edge of the knives has a plurality of facetsthereon, described by angularly successive pairs of dihedral planespassing through the relatively concave face of the edge at acute anglesthereto, so that the edge is scalloped in outline.

17. A rotary chipper drum having a series of cutter knives on thecylindrical cutter surface thereof, each of which projects relativelyoutwardly from the surface of the drum, and has a cutting edge thereonwhich is curvilinear in outline and extends between points coincidentwith spaced parallel longitudinal cross sectional planes of the drum,the relatively concave face of the cutting edge being described by aconical surface of revolution.

18. The rotary chipper drum according to claim 17 wherein each knifeprojects relatively outwardly from the surface of the drum on an axiscoincident with a chord of the drum.

19. The rotary chipper drum according to claim 18 wherein each knife hasan arcuate cutting edge, the relatively concave face of which isdescribed by a conical surface of revolution, the axis of which iscoincident with the chord of the drum.

20. A rotary chipper member having a series of cutter knives on thecutter surface thereof, arranged about the rotary axis thereof, each ofwhich projects rela tively outwardly from the surface of the member, andhas an arcuate cutting edge thereon, the relatively concave face ofwhich is described by a conical surface of revolution.

21. The rotary chipper member according to claim 20 wherein the chippermember takes the form of a drum, and the knives are arranged on chordsof the drum to project relatively outwardly from the cylindrical cuttersurface thereof.

22. A rotary chipper member having recesses in the cutter surfacethereof, arranged about the rotary axis thereof, means defining aplurality of annular blades, each of which is seated in a recess androtatable about the axis of the respective blade, there being aplurality of knives at angularly spaced locations about the blade, andmeans interconnecting the blade and member whereby the blade can befixed in theseated position thereof at orientations corresponding to thelocations of the knives, said knives having an arcuate cutting edgethereon, the relatively concave face of which is described by a conicalsurface of revolution.

23. The rotary chipper drum according to claim 1 wherein the cuttersurface of the drum has a series of recesses therein, and the recesseshave cutter blades seated therein, which define the knives; and whereinthe inner periphery of each of the cutter blades is described by areversedly inclined conical surface of revolution terminating at therelatively concave face of the cutting edge.

24. The rotary chipper drum according to claim 11 wherein the innerperiphery of the blade is described by a reversedly inclined conicalsurface of revolution terminating at the relatively concave face of thecutting edge of the knives.

25. The rotary chipper member according to claim 20 wherein the cuttersurface of the member has a series of recesses therein, and the recesseshave cutter blades seated therein, which define the knives; and whereinthe inner periphery of each of the cutter blades is described by areversedly inclined conical surface of revolution terminating at therelatively concave face of the cutting edge.

26. The rotary chipper member according to claim 22 wherein the innerperiphery of the blade is described by a reversedly inclined conicalsurface of revolution terminating at the relatively concave face of thecutting edge of the knives.

Patent NO hatcd January 14, 1975 Inventor(s) Thomas I 'Anson It iscertified that error appears in the above-identified patent and that:said Letters Patent; are hereby corrected as shown below:

Face sheet page, line 2 "Anson" should read --I'Anson--;

[76] Inventor's name should read "Thomas I'Anson" Signed and sealed thisflat day of June 1975.

5:33,) fittest:

C. IIzaRI-SHALL DAZJE TF C. ILXSUIZ Commissioner of Patents .attestingOfficer and Trademarks

1. A rotary chipper drum having a series of cutter knives on thecylindrical cutter surface thereof, each of which projects relativelyoutwardly from the surface of the drum, and has an arcuate cutting edgethereon, the relatively concave face of which is described by a conicalsurface of revolution.
 2. The rotary chipper drum according to claim 1wherein the relatively concave face of the cutting edge extends over acontinuous arcuate course bounded by the cylindrical surface plane ofthe drum.
 3. The rotary chipper drum according to claim 1 wherein therelatively convex face of the cutting edge has a plurality of facetsthereon, described by angularly successive pairs of dihedral planespassing through the concave face of the edge at acute angles thereto, sothat the edge is scalloped in outline.
 4. The rotary chipper drumaccording to claim 3 wherein the knives project relatively outwardlyfrom the surface of the drum on axes of revolution coincident withprogressively helically advanced chords of the drum.
 5. The rotarychipper drum according to claim 4 wherein those facets of the relativelyconvex faces of the edges which traverse the cross-sectional planes ofthe drum coincident with the chords, are disposed in planes which extendsubstantially parallel to the cylindrical surface plane of the drum; andthe facets adjacent thereto are disposed in planes which extend at equalobtuse angles thereto and intersect the cylindrical surface plane of thedrum.
 6. The rotary chipper drum according to claim 3 wherein each knifeis defined by an annular cutter blade that is seated in a recess in thesurface of the drum, and equipped with a plurality of similar knivesthereon, at angularly spaced locations thereabout.
 7. The rotary chipperdrum according to claim 6 wherein the blade is rotatable about the axisthereof between a plurality of angular orientations corresponding to thelocations of the knives, and there are means interconnecting the bladeand the drum whereby the blade can be fixed in the seated positionthereof at each orientation, for alternate or interchangeable use of theknives thereon.
 8. The rotary chipper drum according to claim 7 whereinthe blade is defined by one end edge portion of an elongated tubularelement which is detachably inserted in the recess and releasablyinterlockable with the drum at each operative orientation of the blade.9. The rotary chipper drum according to claim 8 wherein the recess isdefined by a stationary holder in the surface of the drum, and theelement and holder have cooperable means thereon for fixing the relativeangular and longitudinal positions of the element in the holder at thevarious operative orientations of the blade.
 10. The rotary chipper drumaccording to claim 9 wherein the means for fixing the positions of theelement include cooperating pin and groove means for fixing the positionof the element in one sense, and means threadedly interconnected withthe holder to fix the position of the element in the other sense.
 11. Arotary chipper drum having a recess in the cylindrical cutter surfacethereof, means defining an annular blade which is seated in the recessand rotatable about the axis thereof, there being a plurality of knivesat angularly spaced locations about the blade, and means interconnectingthe blade and drum whereby the blade can be fixed in the seated positionthereof at orientations corresponding to the locations of the knives,said knives having an arcuate cutting edge thereon, the relativelyconcave face of which is described by a conical surface of revolution.12. The rotary chipper drum according to claim 11 wherein the axis ofthe blade is coincident with a chord of the drum, so that a knifeprojects relatively outwardly from the surface of the drum at eachorientation of the blade.
 13. The rotary chipper drum according to claim12 wherein the blade is defined by one end edge portion of an elongatedtubular element which is detachably inserted in the recess andreleasably interlockable with the drum at each operative orientation ofthe blade.
 14. The rotary chipper drum according to claim 13 wherein therecess is defined by a stationary holder in the surface of the drum, andthe element and holder have cooperable means thereon for fixing therelative angular and longitudinal positions of the element in the holderat the various operative orientations of the blade.
 15. The rotarychipper drum according to claim 14 wherein the means for fixing thepositions of the element incluDe cooperating pin and groove means forfixing the position of the element in one sense, and means threadedlyinterconnected with the holder to fix the position of the element in theother sense.
 16. The rotary chipper drum according to claim 13 whereinthe relatively convex face of the cutting edge of the knives has aplurality of facets thereon, described by angularly successive pairs ofdihedral planes passing through the relatively concave face of the edgeat acute angles thereto, so that the edge is scalloped in outline.
 17. Arotary chipper drum having a series of cutter knives on the cylindricalcutter surface thereof, each of which projects relatively outwardly fromthe surface of the drum, and has a cutting edge thereon which iscurvilinear in outline and extends between points coincident with spacedparallel longitudinal cross sectional planes of the drum, the relativelyconcave face of the cutting edge being described by a conical surface ofrevolution.
 18. The rotary chipper drum according to claim 17 whereineach knife projects relatively outwardly from the surface of the drum onan axis coincident with a chord of the drum.
 19. The rotary chipper drumaccording to claim 18 wherein each knife has an arcuate cutting edge,the relatively concave face of which is described by a conical surfaceof revolution, the axis of which is coincident with the chord of thedrum.
 20. A rotary chipper member having a series of cutter knives onthe cutter surface thereof, arranged about the rotary axis thereof, eachof which projects relatively outwardly from the surface of the member,and has an arcuate cutting edge thereon, the relatively concave face ofwhich is described by a conical surface of revolution.
 21. The rotarychipper member according to claim 20 wherein the chipper member takesthe form of a drum, and the knives are arranged on chords of the drum toproject relatively outwardly from the cylindrical cutter surfacethereof.
 22. A rotary chipper member having recesses in the cuttersurface thereof, arranged about the rotary axis thereof, means defininga plurality of annular blades, each of which is seated in a recess androtatable about the axis of the respective blade, there being aplurality of knives at angularly spaced locations about the blade, andmeans interconnecting the blade and member whereby the blade can befixed in the seated position thereof at orientations corresponding tothe locations of the knives, said knives having an arcuate cutting edgethereon, the relatively concave face of which is described by a conicalsurface of revolution.
 23. The rotary chipper drum according to claim 1wherein the cutter surface of the drum has a series of recesses therein,and the recesses have cutter blades seated therein, which define theknives; and wherein the inner periphery of each of the cutter blades isdescribed by a reversedly inclined conical surface of revolutionterminating at the relatively concave face of the cutting edge.
 24. Therotary chipper drum according to claim 11 wherein the inner periphery ofthe blade is described by a reversedly inclined conical surface ofrevolution terminating at the relatively concave face of the cuttingedge of the knives.
 25. The rotary chipper member according to claim 20wherein the cutter surface of the member has a series of recessestherein, and the recesses have cutter blades seated therein, whichdefine the knives; and wherein the inner periphery of each of the cutterblades is described by a reversedly inclined conical surface ofrevolution terminating at the relatively concave face of the cuttingedge.
 26. The rotary chipper member according to claim 22 wherein theinner periphery of the blade is described by a reversedly inclinedconical surface of revolution terminating at the relatively concave faceof the cutting edge of the knives.